Skip to main content

LeBonCoin Chrome Extension

The Steer LeBonCoin Chrome Extension (steer-lbc-extension) allows automotive dealers to import their vehicle listings and high-resolution photo galleries from LeBonCoin into Steer inventory with a single click.

Architecture & Manifest V3​

The extension is engineered to adhere strictly to Google Chrome Manifest V3 and Mozilla Firefox web extension guidelines:

  • Permissions: activeTab (contextual tab inspection) and storage (local secure token caching).
  • Host Permissions: Restricted strictly to https://www.leboncoin.fr/* and https://img.leboncoin.fr/*.
  • Zero Third-Party Proxies: Vehicle metadata and image downloads are performed locally within the dealer's authenticated browser context.

Installation & Pairing​

  1. Install the Extension: Install the extension from the Chrome Web Store or load the unpacked build directory in Chrome via chrome://extensions (Developer Mode).
  2. Obtain Pairing Nonce: Open your Steer dashboard and navigate to Cars › Import my stock › Import from a portal › Leboncoin. Steer generates an ephemeral pairing session and a 32-byte cryptographic nonce (X-Import-Nonce) via POST /api/v1/dms/portal-import/sessions.
  3. Authenticate Extension: Click the Steer icon in the browser toolbar and enter the pairing code. Once paired, the extension communicates securely with your Steer dealership tenant.

1-Click Vehicle Scraping Workflow​

  1. Navigate to your dealer listings page on LeBonCoin (/compte/pro/mes-annonces, /compte/part/mes-annonces, or /pro/dashboard).
  2. Open the listing of the vehicle you wish to import into Steer.
  3. Click the Import to Steer floating button rendered by the extension.
  4. The extension extracts vehicle attributes automatically:
    • Make, Model, Version, and Commercial Trim.
    • First registration date, model year, and recorded odometer mileage.
    • Engine type, fuel classification, transmission type, and power.
    • Full vehicle listing description and itemized equipment list.
    • Asking price in EUR.

Direct S3 Photo Upload​

To maximize transfer speed and protect privacy, photo ingestion bypasses server proxies entirely:

  1. The extension downloads original high-resolution photo binaries directly inside the dealer's browser.
  2. It requests presigned Amazon S3 upload URLs from the Steer backend using the active session nonce (POST /api/v1/dms/portal-import/sessions/:id/photo-upload-urls).
  3. Images are uploaded directly from the browser to S3 across 4 parallel threads with 3 automatic retries per image.
  4. The Steer backend server never connects to LeBonCoin CDN servers, ensuring compliance with portal terms.

Ownership Verification & Security Safeguards​

To prevent unauthorized listing scraping and ensure legal compliance:

  • Owner-Only Gating: The extension functions only on authenticated owner account pages. It cannot be executed on third-party competitor listings.
  • SIRET Match: The SIRET number on the LeBonCoin professional account must match the company registration in Steer, or pass a verification code challenge (STEER-XXXX).
  • Legal Attestation: Before completing import, the dealer must confirm an attestation checkbox declaring legal ownership of the vehicle listing.
  • Account Unicity: Accounts are securely fingerprinted with HMAC-SHA256 (PORTAL_IMPORT_HASH_SECRET) to prevent duplicate tenant assignments.
  • Feature Flag: Controlled via the backend environment flag PORTAL_IMPORT_LEBONCOIN_ENABLED.